Fluid pressure brake



April 26, 1938.

Filed Sept. 14, 1955 R R Y N d w Wm mm 0^ \\m. Q mm m w A f I L. m Pw MWMWWH M c m f- 0 .b w. gfx @m 1r M w Q.; Am wm \\h. W9 lill/ll l@ Q.. m whllln/Vww @m www w, E g Wm mmmnwlm-@IWCL m. /vfwm Q mm mm www# V mhf wm Patented Apr. ze, 193s y 2,115,551 l UNITED STATES PATENT OFFICEl FLUID PRESSURE BRAKE f Clyde C. Farmer, Pittsburgh, Pa., signor .to

The Westinghouse Air Brake Company, Wilmerding, Pa., a corporation o! Pennsylvania Application September 14, 1935, BeriaiNo. 40,611

"" '7 Claims. (Cl. 18S-152) This invention relates to fluid pressure brakes the sides of the housing projecting from a back y and more particularly to the type in which pneuplate 2 which is journaled von an axle 3 adapted matic or hydraulic pressure is adapted to be to be braked. An arm l projects from one of the applied to brake shoes for pressing the brake sides of the housing and is adapted to be secured 5 shoes against a member to be braked. to any stationary part of a vehicle for holding 5 One' object of the invention is to provide an the housing I against rotation with the axle 3. improved brake system of the above type in which A brake drum 5 is disposed within the housing 1 a relatively low actuating pressure' will produce a I and Is secured to the end of axle 3 so as to turn relatively high braking effect. with the axle. Fourequally spaced brake shoes A more specific object of the invention is to 6 are disposed Within the yhousing I around the 10 provide an improved brake system of the above drum 5 and concentric with said drum. Each of type having a plurality of closely spaced, radially these brake shoes is provided with an opening 1. movable brake shoes arranged around a brake through which a lug 8 extends, the lug 8 being drum or the like and movable by pressure applied secured to the back plate 2. The thicknessof the uniformly over the area of one side into frictional lug 8 is such with respect to the width of the open- 15 engagement with the drum for braking the drum, ings 'l through the shoes as to permit free radial the combined length of the braking surfaces on movementof the shoes relative to the drum 5, the shoes being equal to the major portion of the while the width of the lugs is such with respect to circumference of the drum, and the area which is the opening 1 as to prevent appreciable movement subjected to pressure for pressing the shoe against of the shoes in the direction of rotation of the the drum is greater than the area of the drum drum 5. Thel shoes 6 may be held in place on engaging surface of the shoe, whereby a rela'.- their respective lugs in any suitable manner, such tively low unit pressure applied to the shoe will for instance, as by keys 9 which may be secured produce a relatively high unit pressure against to said lugs by being driven into suitable lopenthe drum. ings or in anyk other desired manner. 25

Another object of the invention is to provide an The inner surface of the brake shoes is shaped improved braking mechanism such as just dened to conform to the outside diameter of the brake in which the width of the area to which pressure is drum 2,- and secured to this surface is a brake applied is no greater than that of the braking lining I0 adapted to frictionally engage the outer surface of theshoeor than that of the drum. periphery of said drum. 30 A still further object of the invention is to pro- The end faces of the brake shoes are substanvideln a brake mechanism of the above type in tially parallel and extend substantially radially which a flexible diaphragm like tube is employed of the drum. In both of these end faces is proas the medium for applying pressure to each of vided apocket II, the pocket II in one shoe being the brake shoes, a relatively simple system for opposite the pocket on the adjacent end of the 35 adjusting the normal clearance space between the adjacent shoe. A spring I2 is provided between braking surface of the brake shoes and the memthe adjacent ends of each two shoes with one end ber to be braked, and for thereby limiting the exin the pocket I I in one shoe and the other end in pansion of the diaphragm like tube in moving the the pocket I I in theadjacent shoe. The several brake shoes into braking engagement with said springs I2 are under compression and coact to V.1() member, and further for equalizing said clearurge the several shoes outwardly on their respecance space and diaphragm travel for the several tive lugs 8 and thus away from the brake drum 5. brake shoes and diaphragms. A flexible tube-like diaphragm I5, to be here- Other objects and advantages will be apparent inafter described, engages the pressure receiving from the following more detailed vdescription of face of each shoe 6 anda pair of oppositely dis- 45 the invention. posed coacting wedges I3 and I4 are disposed be' g In the accompanying drawing; gig. 1 is a crosstween each shoe and the casing for limiting the sectional view, with certainparts shown in outextent of outward movement of the shoes, and line, of a braking mechanism embodying the invthereby the clearance space between the brake vention; and Fig. 2 is in part a side elevational drum 5 and the brake lining I0, due to the action 50 view of the mechanism shown in Fig. 1, and in of springs I2. part a sectional view taken on the line 2-2 of -Each of the wedges I3 has one face in engage- Fig, `1 ment with .the casing I and has an opposite and As shown in the drawing, the braking mechainclined face I6, while each of the wedges I4 has nism comprises a four sided, box-like housing I, one face in engagement with its respective dia- 55 phragm I4 and an opposite and inclined face I1 adapted to slidably engage the face I4 on the coacting wedge I 4.

One end of each of the wedges I4 is provided with a bore which freely receives a pin I4 secured in the casing I, so that the pin acts to prevent movement of the wedges I4 relative to the casing except in a direction toward the brake drum 4.

An adjusting screw I4 is provided for each of the wedges I 2 for individually moving said wedges relative to the casing and y.the coacting wedge I4. Each o1' the adjusting screws I8 extends through a suitable opening in the casing and has screwthreaded engagement therewith. Inside oi the casing, each oi the screws extends into a bore in one end of the respective wedge I3. In this bore the end of the respective screw is pivotally connected to the wedge I2 by asnap ring 2l. Each of the adjusting screws Ilvis provided outside of the casing with a head 2l for receiving a wrench or the like, and a lock nut 22 adapted to engage the casing for locking the screw in an adjusted position.

The diaphragms I4 are preferably made of metal and are normally in the i'orm oi a ilattened expansible tube closed at both ends and thereby forming a iluid receiving chamber 24 which is open to a pipe 24. 'Ihe pipe 24 extends through a suitable opening in the wedge I4 and an elongated slot 24 in the wedge Il. The several pipes 24 connecting to the several diaphragm chambers 22 are all connected outside of the casing I to a common pipe 26 through which fluid under pressure is adapted to be supplied to and released from said chambers.

In operation, in order to apply the brake shoes 4 to the drum 4 for braking the axle 2, iluid under pressure is supplied in pipe 24 and from thence flows through the several pipes 24 to chamber 23 inside each of the diaphragms I4. 'Ihe pressure of iluid obtained in the chambers 24 acts to simultaneously expand the diaphragm I4 between the inner wedges I4 and the brake shoes 4. Since the wedges I4 are ilxed with respect to the casing, the expansion` oi the diaphragms I4 moves the shoes 4 into frictionai engagement with the brake drum 4 and exerts thereon a retarding force proportional to that applied in chamber 24.

In order to release the brake shoes 4 irom the brake drum 4, huid under pressure is released from pipe 24 and thereby irom diaphragm` chambers 23, through the pipes 24. This permits the diaphragms I4 to contract and thereby return to their original or normal form which in turn permits the springs I2 to force the shoes 4 apart and thus move said shoes out of braking engagement with the drum l.

It will benotedthattheareaof thefaceoi.' the brake shoes 4 which is engaged by the diaphragms I4 is greater than the area of the brake shoe lining I4 which is adapted to engage the drum 4, and it will be further noted that the combined areas ot the surface of the several shoes engaged by the several diaphragms is greater than the area of the exterior surface oi the drum, so that a relativelylow unit pressure applied to the shoes by the dlaphragms will produce relative high unit pressure between the shoes and drum. 'Ihis is very desirable in that it permits the use of relatively low huid pressures in the diapbragms which reduces the possibility of diaphragm rupture and provides for longer diaphragm lite.

It should be further noted that the i'ace oi' the brake shoes engaged bythe diaphragms is no greater in width than that of the drum or brake lining on the shoes, and that the greater shoe area for engagement with the diaphragms is obtained by mounting the brake shoes around the exterior of the drum. Furthermore, the shoes are of such length as to engage the major portion of the periphery of the drum and this provides a system in which relatively low shoe pressures against the drum will provide a relatively high retarding eiect on the drum.

It will be noted that in releasing the brakes, the springs I2 cause the brake shoes 4to follow the diaphragms I4 as they are deflated, so that the release position of the shoes is defined by the position of the wedges I4 and I4 and the normal overall thickness of the diaphragms I5 which are interposed between said wedges and the shoes. In other words the wedges I3 and I4 and the thickness oi. diaphragm I5 deilne the clearance space between the shoe lining I and the brake drum 4.

It is desirable that this clearance space be maintained within certain limits particularly in order to prevent excessive expansion and thereby over stressing of the diaphragm I when applying the brakes.

Wear of the brake lining III and drum 5 will cause an increase in this clearance space. In

order to adjust this clearance space a cover 21 is removed from the casing to gain access to the drum 4 and shoes 4. 'I'he lock nuts 22 on the adjusting screws I4 are then released and the screws I are turned into the casing I which forces the wedges I4 into the space between the casing and the wedges I4. The wedges I4 are prevented i'rom moving with the wedges I2 due to the pins I4, but the wedging action resulting from movement of wedges I4 forces the wedges I4, diaphragms I4 and brake shoes 4 inwardly toward the brake drum 4. A ieeler gauge or the like may be used to determine the clearance between the brake drum and brake lining, and when the shoes 4 are forced inwardly suniciently to obtain the desired clearance, then the lock nuts 22 are turned against the casing to lock the screws Il and thereby wedges I4 and I4,. diaphragms I4 and shoes 4 in their adjusted position. after which the cover 2'I is again applied to the casing.

It will be evident that each shoe 4 is adapted to be individually adjusted by means of one o! the screws I4 and one set of wedges I4 and I4. so that if for any reason the clearance of one shoe. prior to adjustment, should be diil'erent from that ot another shoe, all shoes may be adjusted .to provide the same clearance space.

It should be noted that by using the wedges I4 and I4 for adjusting purposes, and permitting the wedges I4 to move only in a direction radially oi the brake drum, the shoes are maintained in the proper concentric relation with the drum, and the diaphragm I4 are not distorted in any way during the adjusting process.

In order to apply new shoes when desired. the cover plate 21 is removed from the casing I and the adjusting screws I4 are backed out of said casing. This pulls the wedges Il away from the wedges I4 and permits the pressure of springs I2 to urge the brake shoes 4, diaphragms I4 and wedges I4 outwardly. 'I'he screws I4 may be thus released until the thicker end of wedge I4 engages the casing. The keys l are removed from the ends of the lugs 4 and then the shoes 4. are pulled on of said lugs. New shoes or reconditioned shoes are then applied to the lugs with the springs I2 properly positioned in the ends of the shoes.' The keysS are then reappiied and the brake shoe clearance adjusted as hereinbefore described following which the cover f plate 21 is again secured to the casing.

While in the description of operation' fluid under pressure has been referred to as the brake control medium, it will be evident that this control may be either in the form of a compressed gas or a column of liquid to which pressure may be applied.

While one illustrative embodiment of the invention has been described in detail, it is not my intention to limit its scope to that embodiment or otherwise than by the terms of the appended claims. i

Having now described my invention, what I claim as new and desire to secure by Letters Pat-` ent, is:

1. In a fluid pressure brake, in combination, a casing, a rotatable braking drum in said casing, a braking element adapted to frictionally engage said drum, an expansible tube engaging said element and operable upon supplying fluid under pressure to said tube to press said element into engagement with said drum, means for adjusting the normal clearance space between said element and drum, and means carried by said casing oprable to lock said adjusting means and thereby said element in an adjusted position.

2. In a iluid pressure brake, in combination, a casing, a rotatable brakedrum in said casing, a braking element adapted to frictionaliy engage said drum, an expansible tube engaging said element and operable by fluid under pressure to press said element into fr-ictional engagement with said drum, means interposed between said casing and said tube for adjusting the normal clearance splace between said element and said drum, and means for locking the adjusting means to said casing for thereby securing said braking element in an adjusted position.

3. In a fiuid pressure brake, in combination, a casing, a rotatable brake drum, a braking element adapted to frictionally engage said drum, an expansible tube engaging said element and operable by fluid under pressure to press said element into frlctional engagement with said drum,

a pair of cooperating wedges interposed between said casing and said tube, and manually operable means for moving one wedge relative to the other, to adjust the position of said tube and element relative to said drum.

4. In a fluid pressure brake, in combination, a casing, a rotatable brake drum, a braking element adapted to frictionaily engage said drum, an expansible tube engaging said element and operable by fluid under pressure to press said element into frictional engagement with said drum,

a pair of cooperating movable wedges interposedv between said casing and said tube, with one wedge engaging said casing and the other engaging said tube, means for 'moving the wedge engaging the casing relative to the other wedge for adjusting the position of said tube and element relative to said drum, and means for preventing movement of the wedge engaging said tube relative to said tube.

5. In a fiuid pressure brake, in combination, a. casing, a rotatable brake drum in said casing, a plurality of brake elements arranged around the exterior circumference of said drum and adapted to be moved into frictional engagement with said drum, an expansible tube engaging each element and operable by fluid under pressure for moving the corresponding element into engagement with said drum, spring meansl operable upon the relief of uid under pressure from said tubes for moving said elements away from said drum, stop means for dening the extent of movement of each element by said spring means, means in s aid casing for adjusting said stop means and thereby the clearance space between said braking elements and drum when said tubes are relieved of fluid under pressure. and meanscarried by said casing for locking said adjusting means and thereby said braking elements in an adjusted position.

6. In av fluid pressure brake, in combination, a casing, a rotatable member in said casing adapted to be braked, a brake element normally spaced from said member and movable into braking engagement therewith, expansible means operative by fluid under pressure for moving said brake element into engagement with said member, means screwthreaded in said casing and operable to move said expansible means 'and brake element relative to said member for adjusting the distance said brake element is normally spaced from said rotatable member, and means for locking said screw-threaded means to said casing for thereby locking said brake element in an adjusted condition.

7. In a fluid pressure brake, in combination, means fixed against rotation, aV rotatable member adapted to be braked, a brake element normally spaced from said member and movable into braking engagement therewith, adjustable means, expansible means, said adjustable means and expansible means being disposed between said brake element 'and the xed means in engagement with each other and with one engaging said brake element and the other engaging said fixed means, said expansible means being operative by uid underv pressure to move said brake 4element into engagement with said member, resilient means for moving said brake element away from said member upon contraction of@ said expansible means, and means for operating said adjustable means to adjust the distance said resilient means moves said brake element away from said brake member.

CLYDE C. FARMER.

Patent NQ. 2,115,551.

CERTIFICATE oF CORRECTION.

. April 26, 1958.

CLYDE C. FARMER. It is.hereby certified that error appears in the printed specification of the above numbered patent requiring correctnmiaafbllows: Page, sec? ond column, line 18, clain15, after "means".insert the words in said casing; and that the said Letters Patent shouhberad with this correction therein that the same may conform totherecord.of`the case in the Patent Office. Y l

Signed and sealed this 26th day of September, A. D. 1959.

` Henry Van Arsdale, (Seal) Acting Commissioner of Patents. 

